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How to perform comparision in unix

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# 1  
Old 02-02-2005
How to perform comparision in unix
I am trying to perform a simple if/else check.

if [ $CON_DIR=="" ]; then
mkdir /wdnet/oracletest
else
mkdir $CON_DIR
fi

I guess I don't understand the unix basics about comparisons.
My scripts always executes the if, even though my CON_DIR variable is not blank.
What am I doing wrong?
# 2  
Old 02-02-2005
Try:
if [ "$DIR_CON" = "" ]

With the [ style of if, the variable must be quoted so it will work if it is blank. A single = not == is needed. And blanks must separate everything from each other.
# 3  
Old 02-02-2005
Code:
#!/usr/bin/ksh

str=""

if test $str==""
 then
   echo "YES"
 else
   echo "NO"
fi

if [ $str==""  ]
then
    echo "YES"
else
    echo "NO"
fi

if test -z "$str"
then
    echo "YES"
else
    echo "NO"
fi

if ! test -n "$str"
then
    echo "YES"
else
    echo "NO"
fi

# 4  
Old 02-02-2005
Change
str=""
to
str="something"
and try it again. Smilie
# 5  
Old 02-02-2005
Thanks Perderabo ! for pointing this out ....
Following works out for null and non-null strings.


Code:
#!/usr/bin/ksh

str="something"

if test "$str" = ""
 then
   echo "YES"
 else
   echo "NO"
fi

if [ "$str" = ""  ]
then
    echo "YES"
else
    echo "NO"
fi

if test -z "$str"
then
    echo "YES"
else
    echo "NO"
fi

if ! test -n "$str"
then
    echo "YES"
else
    echo "NO"
fi

# 6  
Old 02-03-2005
Thanks perderabo.

I got this working yesterday, but I my id must have been new and would not let me log back in.
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